I've never read the book, but I've heard mixed reviews of it. Some people I know really like it, others hate it.

The movie by itself was good. Yeah, the transformation sequences looked like the SFx team kinda got tired towards the end, but other than that it was good.
However, if you took the amount of stuff from the book that the movie actually covered (everything from plot to character histories), it would total up to *maybe* 2.5 pages. Standard print, not that tiny-ass font. Which... is kinda sad. O.o
For example: The movie is set in Romania. The book is set in the U.S., and never leaves the country. Most of the Pack members are actually of Germanic/English or French extraction (two of the main characters are Vivian Gandillon and her mother Esme... definitely French-ish, yes?)

But enough of my rambling about it. ^^;;; Like I said, the movie is good by itself. The book is also excellent and I'd recommend it highly. Mine is just one opinion; your own is the best to rely on. ^^

Sometimes I wonder why converting a book to movie form always changes so much. Maybe Hollywood has to "improve" the story to make it more entertaining to a movie crowd? :/

Yeah... I guess they figure everyone who's read the book has already "seen" it in their imagination, so they have to make it different somehow... *shakes head* They should really say "Based loosely on a liberal interpretation of the book...". Ah well. I guess that gives actual fans of the book with the means a reason to make their own version, eh? Hehe.